The Neuropathology Core, Core 2, will maintain a bank of central nervous system (CNS) tissues from children who died with HIV-1 infection, including both frozen and fixed tissues. Snap frozen tissue blocks are currently available from 25 cases, and there are also formalin-fixed, paraffin-embedded tissue blocks from these cases as well as from another 50 cases. It is anticipated that up to five new autopsy cases of children with AIDS, coming from the Pediatric AIDS Clinical Trials at University Hospital, will be accessioned by the tissue bank for each year of the project. Tissues will also be obtained from HIV-1-negative control cases. Furthermore, CNS tissue specimens will also be obtained from HIV-1- infected and HIV-1 negative adults who come to autopsy at University Hospital. Finally, tissues will be made available to the Core from the Neuropathology Division of Columbia-Presbyterian Medical Center in New York, both from HIV-1 infected and HIV-1 negative autopsies. The anticipated number of HIV-1 infected adult cases is up to 10 per year. The Core will supply tissue specimens to the various Projects as needed. In addition, the Core will provide neuropathology support and tissue immunocytochemistry and HIV-1 in situ-PCR services to the Projects. The PI, Dr. Leroy Sharer, will continue a survey of CNS tissues for the presence of HIV-1, using in situ-PCR. In addition, he will continue to monitor neuropathological changes in the pediatric cases coming to postmortem examination, with particular emphasis on the occurrence of HIV- 1 encephalitis and its relationship to anti-retroviral therapy.